An air-circulating vacuum cleaner is designed so that air is sucked into a suction port of a suction nozzle by operating a motor blower, the sucked air is run through a filter so that dust therein is seized, the air run through the filter and discharged from the motor blower is returned to the suction port, and the returned air is recovered through the suction port and circulated for cleaning. Thus, exhaust gas that contains dust, germs, etc. can scarcely be discharged to the outside, so that the cleaner has advantages in being more sanitary and less power-consuming.
In the circulating vacuum cleaner of this type, moreover, the circulated exhaust blast is blown against a floor surface so that dust on the floor surface can be flung up and sucked in. Thus, the dust collecting efficiency of this cleaner is high. Since the circulated exhaust blast is heated to high temperature, furthermore, harmful microorganisms, such as various germs, ticks, etc., in a dust chamber can be killed or wounded, so that better hygiene is ensured.
Vacuum cleaners of this type are disclosed in Jpn. UM Appln. KOKOKU Publication No. 39-36553, Jpn. Pat. Appln. KOKAI Publication No. 3-162814, etc.
According to these vacuum cleaners, an exhaust blast is blown off into the suction port of the suction nozzle, dust on a floor surface is flung up by the exhaust blast, and the exhaust blast, along with the dust, is sucked again into the motor blower. However, all the exhaust blast that is blown off into the suction port is not always sucked again into the motor blower in the aforesaid manner, and sometimes may leak out from between the suction nozzle and the floor surface. If the exhaust blast leaks out in this manner, the dust on the floor surface around the suction nozzle is blown away and scattered, so that the cleaning efficiency lowers inevitably. In the case where the floor surface to be cleaned is a smooth floor surface, such as a wooden floor surface, in particular, the exhaust blast easily leaks out through the gap between the suction nozzle and the floor surface. When the suction nozzle is lifted from the floor surface, moreover, the exhaust blast is liable to be blown off to the outside in the aforesaid manner.
Described in Jpn. Pat. Appln. KOKAI Publication No. 3-162814, etc., moreover, is a suction nozzle that has therein a cleaning rotor, which is rotated by utilizing the energy of the exhaust blast that is discharged from the motor blower and returned to the suction port. According to this suction nozzle, having the cleaning rotor therein, the cleaning rotor taps the floor surface to fling up dust thereon, so that the cleaning efficiency is high enough. Since the exhaust blast rotates in the suction port, the exhaust blast forms a turbulent flow in the suction port and easily leaks out through the gap between the suction nozzle and the floor surface.
When the suction nozzle having the cleaning rotor is lifted from the floor surface, furthermore, no resistance acts on the cleaning rotor, so that the cleaning rotor races at high speed, sometimes producing loud noises.
A brush or a rubber lip member that protrudes from the underside of a suction nozzle to prevent the exhaust blast from leaking to the outside is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 61-2821, Jpn. UM Appln. KOKAI Publication No. 51-154065, etc.
Although the bristles of the brush and the projecting lip member have an effect to prevent the leakage of the exhaust blast to the outside, however, they may possibly push aside dust on a floor surface when the suction nozzle is moved on the floor surface, thus lowering the cleaning efficiency.